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Adding 9, 19 and 99 Mental Maths Worksheet

Mental maths lesson 4: Add and take away 9, 19 and 99 · Set 863 · 40 questions
TalentJR

How to do it in your head (Round and adjust): Add 9, 19, 99: add 10, 20, 100, then take 1 away. Take away 9, 19, 99: take away 10, 20, 100, then add 1 back. Ask yourself: did I use too much or too little?

NameDateTime takenScore ___ / 40
  1. 1.58 + 9 =
  2. 2.55 − 19 =
  3. 3.86 − 19 =
  4. 4.66 − 29 =
  5. 5.660 + 99 =
  6. 6.64 − 9 =
  7. 7.757 + 99 =
  8. 8.64 + 9 =
  9. 9.77 + 9 =
  10. 10.649 − 99 =
  11. 11.18 + 19 =
  12. 12.707 + 99 =
  13. 13.629 + 99 =
  14. 14.95 − 19 =
  15. 15.189 + 99 =
  16. 16.492 − 99 =
  17. 17.739 − 99 =
  18. 18.53 + 9 =
  19. 19.70 − 29 =
  20. 20.521 + 99 =
  21. 21.56 − 29 =
  22. 22.469 + 99 =
  23. 23.66 + 29 =
  24. 24.818 − 99 =
  25. 25.84 − 19 =
  26. 26.69 + 19 =
  27. 27.41 − 29 =
  28. 28.57 + 29 =
  29. 29.68 + 29 =
  30. 30.43 + 29 =
  31. 31.52 − 9 =
  32. 32.54 − 29 =
  33. 33.29 + 9 =
  34. 34.18 + 9 =
  35. 35.16 − 9 =
  36. 36.24 + 19 =
  37. 37.531 + 99 =
  38. 38.45 − 29 =
  39. 39.100 − 29 =
  40. 40.99 − 29 =

Answer key

  1. 67
  2. 36
  3. 67
  4. 37
  5. 759
  6. 55
  7. 856
  8. 73
  9. 86
  10. 550
  11. 37
  12. 806
  13. 728
  14. 76
  15. 288
  16. 393
  17. 640
  18. 62
  19. 41
  20. 620
  21. 27
  22. 568
  23. 95
  24. 719
  25. 65
  26. 88
  27. 12
  28. 86
  29. 97
  30. 72
  31. 43
  32. 25
  33. 38
  34. 27
  35. 7
  36. 43
  37. 630
  38. 16
  39. 71
  40. 70

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